Very often during the construction of a building, it is necessary for a worker to perform work at an elevated position above the ground, e.g. greater than three meters above the ground. One example of such an activity is where a worker is required to work on a roof structure. This will involve lifting I-beams which form the roof rafters up onto the roof and then mounting them on the basic frame of the building. Thereafter roof purlins extending the length of the roof are mounted on the rafters transverse thereto and sheeting is then applied to the purlins.
As can be seen this process requires workers to perform difficult and precise operations while they are perched high up on a beam or other structural member. It is quite possible that they could slip and fall and the consequences of this could be disastrous. Accordingly it is highly desirable that workers be provided with safety apparatus to help them to avoid suffering serious injury or death should they fall. This has been recognized by the authorities around the world who require safety apparatus to be provided for such workers. There is now an Australian standard in place for these types of safety apparatus that is Australian Standard No. 1891.2.2000.
Various forms of safety apparatuses have been proposed to improve the safety of workers working on elevated structures.
One such example is in the form of a temporary rail or barrier around the periphery of a structure having a roof. This works by acting as a physical barrier to stop a worker from falling over the edge of the building if they slip. However the limitation of this apparatus is obvious. It does not physically tether a worker to the structure and does not arrest their fall if they fall off a building. It is limited to horizontal or sloping roof structures where the roof sheeting or roof tiles are already in place. It has little or no benefit in an open frame structure where a worker can fall through the internal space defined by the building.
Safety apparatuses are also known where a worker is connected to or tethered to a safety line. However, many of these apparatuses do not offer a worker sufficient freedom to move around and do their work efficaciously. Further there are considerable difficulties in achieving the necessary mechanical strength to arrest the fall of an adult male worker. Part of the problem is that the safety apparatus is usually a temporary structure which is mounted on a roof, e.g. by being attached to a beam, and which has to be light enough to be lifted onto the roof. Further it also needs to provide a worker with satisfactory mobility over a roof area and also not inhibit their working activities.
In Applicant's experience very often apparatus of this general type is not strong enough to arrest the fall of a stout adult male weighing 70–100 kg.
Thus there are a large number of criteria to meet when designing such a system and a satisfactory solution to the problem has been elusive. Accordingly it would clearly be advantageous if an apparatus could be devised that overcame the problem.